That may vary per game though. BioWare has generally been pretty good about ensuring those who hack their game files in the Mass Effect 3 multiplayer get promptly banned. Of course, it probably helps that the business model for the ME3MP relies on microtransactions from the store, and people who can get easy credits by making the game much easier won't need to spend money (of course, I don't spend money anyway but that's besides the point).
By contrast, the console versions of ME3 have had missile glitchers as a real problem (there is a glitch you can exploit that makes certain weapons shoot infinite cobra missiles (which is supposed to be a very limited supply heavy weapon), making the game beyond easy). BW have had a much harder time cracking down on this glitch. It's apparently also possible to pull off on PC but much harder and I've never seen it.
And of course the keyboard/mouse controls for ME3 are way better than the gamepad controls. PC gaming master race FTW!